[Qemu-block] [PATCH 4/4] iotests: Test driver whitelisting in 136

[Max Reitz]

null-aio may not be whitelisted.  If it is not, fall back to null-co.
This may run tests twice in the same configuration, but this is the
simplest way to effectively skip the tests in setUp() (without changing
the output, and while having the respective driver in a class
attribute).

Signed-off-by: Max Reitz <address@hidden>
---
 tests/qemu-iotests/136 | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/tests/qemu-iotests/136 b/tests/qemu-iotests/136
index af7ffa4540..44e3bc1575 100755
--- a/tests/qemu-iotests/136
+++ b/tests/qemu-iotests/136
@@ -28,9 +28,11 @@ op_latency = nsec_per_sec // 1000 # See qtest_latency_ns in 
accounting.c
 bad_sector = 8192
 bad_offset = bad_sector * 512
 blkdebug_file = os.path.join(iotests.test_dir, 'blkdebug.conf')
+supported_null_drivers = list(filter(lambda f: f.startswith('null-'),
+                                     iotests.supported_formats()))
 
 class BlockDeviceStatsTestCase(iotests.QMPTestCase):
-    test_img = "null-aio://"
+    test_driver = "null-aio"
     total_rd_bytes = 0
     total_rd_ops = 0
     total_wr_bytes = 0
@@ -68,6 +70,11 @@ sector = "%d"
         file.close()
 
     def setUp(self):
+        global supported_null_drivers
+        if self.test_driver not in supported_null_drivers:
+            # Silently fall back to supported driver
+            self.test_driver = supported_null_drivers[0]
+
         drive_args = []
         drive_args.append("stats-intervals.0=%d" % interval_length)
         drive_args.append("stats-account-invalid=%s" %
@@ -75,8 +82,8 @@ sector = "%d"
         drive_args.append("stats-account-failed=%s" %
                           (self.account_failed and "on" or "off"))
         self.create_blkdebug_file()
-        self.vm = iotests.VM().add_drive('blkdebug:%s:%s' %
-                                         (blkdebug_file, self.test_img),
+        self.vm = iotests.VM().add_drive('blkdebug:%s:%s://' %
+                                         (blkdebug_file, self.test_driver),
                                          ','.join(drive_args))
         self.vm.launch()
         # Set an initial value for the clock
@@ -336,7 +343,9 @@ class 
BlockDeviceStatsTestAccountBoth(BlockDeviceStatsTestCase):
     account_failed = True
 
 class BlockDeviceStatsTestCoroutine(BlockDeviceStatsTestCase):
-    test_img = "null-co://"
+    test_driver = "null-co"
 
 if __name__ == '__main__':
+    if 'null-co' not in supported_null_drivers:
+        iotests.notrun('null-co driver support missing')
     iotests.main(supported_fmts=["raw"])
-- 
2.21.0